The primary research objectives for the forthcoming year are: 1. To find trematodes that are strongly dominant over Schistosoma mansoni for use in field trials in the future. 2. To study the tissue reactions, the role of amebocytes, and the possible role of humoral faction in acquired resistance to trematode infections (echinostomes) in Biomphalaria glabrata. 3. To find a method of inducing resistance to Schistosoma mansoni in B. glabrata snails.